Just as police need evidence of a crime to begin an investigation, T cells must recognize a specific antigen before they start to fight an infection. Dendritic cells constantly scour the body for antigens and present these to T cells for review in the lymph nodes. It is a demanding job. "Just 10 dendritic cells can show viral antigens to over a million T cells in a day," says Dr. Dustin.
Once a T cell's antigen receptor finds an antigen match, the T cell forms an immunological synapse with a dendritic cell through which it queries the dendritic cell for additional information about the antigen and its source in the body. Is the antigen a danger or simply a harmless food protein? The interrogation may last hours, and if the antigen is deemed a threat the T cell starts multiplying, eventually producing thousands of copies of itself. These T cell clones are capable of killing invaders outright and marshaling other cells to destroy them.
In the new study, Gabriele Campi, a graduate student in Dr. Dustin's laboratory, and Kaspar Mossman, a graduate student of Dr. Groves's, created a synthetic dendritic cell using purified antigen and adhesion molecules (molecules that the cell can grip) in a thin fluid coating on a glass surface. In prior studies the antigen was free to move over the entire glass surface, but in this study they set up miniscule chrome barriers, allowing them to modify the pattern of T-cell antigen receptor clusters in the immunological synapse.
Previous research has shown that T cell receptors cluster in a bull's eye-pattern at the interface between the T cell and the synthetic dendritic cell but the significance of this arrangement has been unknown. Thanks to the chrome barriers, Dr. Dustin and his colleagues discovered that the T cell receptor signal is strong
Source:New York University Medical Center and School of Medicine